High throughput time-stretch near infrared spectrometry of low transmittance samples via optical waveguide

Time-stretch spectroscopy has the potential for high-speed inspection application. Currently, the low output power of chirped pulses limits the throughput and targets. We applied Arrayed Waveguide Gratings (AWGs) to time-stretch spectroscopy and achieved a high output power of 90 mW, which is about ten times higher than conventional method. In this study, we performed Near-Infrared (NIR) spectroscopy of low-transmittance samples with the developed time-stretch spectrometer. The absorbance spectrum of liquid samples was measured within ⪅1 ms/sample even with an optical attenuation by an ND filter (OD 3.8). In addition, we can estimate the volume fraction of highly scattering samples with a high accuracy (R² = 0.996) in approximately 5 ms. This result demonstrates the potential of our spectrometer for quantitative spectral analysis of highly scattering samples.